In today's business climate, industry fortunes rise and fall on whether information is exchanged in an efficient manner. For example, cell phones, pagers, and the Internet have thrived because each technology allows businesses to exchange critical market information at a moment's notice. In addition, such technologies allow individuals to keep abreast of recent developments with family and friends. In short, many segments of our modern society require instant access to accurate, up-to-the-minute information.
Companies spend significant resources to develop modern communication systems that provide people with such information. As networked communication systems have matured, data rates have increased from 20 kilobits per second (kb/s) in 1975, to 100 Mb/s with modern VDSL. In other words, customers in today's “information age” can receive data approximately 5,000 times as fast as network customers of thirty years ago. To bring customers into this modern “information age”, developers have spent billions of dollars to develop network technology as we now know it. To continue to increase data rates at such a remarkable pace, communication systems developers will likely be required to spend significant capital resources for many years to come.
When such high speed data arrives at a customer premises (e.g., a individual's home or office), a point-to-multipoint network can distribute that high-speed data to various user devices (e.g., TV sets, computers, video conferencing devices, etc.) Thus, a point-to-multipoint communication system can distribute high-speed or broadband data to multiple network nodes.
In existing point-to-multipoint communication systems (e.g., home networks), multiple network nodes cause signal reflections that can significantly increase signal attenuation. Reflections in these communication systems result in the additions of data signals (e.g., data symbols), and can ultimately cause the signals to spread over time. Due to reflections, signal attenuation might be very different from one network node to another. Further, any change in network configuration (e.g., addition or removal of a network node), may change the attenuation between all other nodes because it changes the signal reflected from this node. Thus, point-to-multipoint communication systems are very dynamic, and the transmission technology used to transmit high-speed data should be capable of adjusting its parameters quickly to adapt to changes in the system.
Existing communication systems that use continuous transmission mode (e.g., DSL, ADSL, VDSL) are advantageous because they have relatively high data rates due to extensive training prior to the data transmission. However, these existing systems suffer from a major drawback in point-to-multipoint communication systems because they must undergo extensive re-training to adapt to considerable changes in channel characteristics. This re-training takes a rather long time (e.g., approximately 30 seconds), and as such makes continuous transmission mode data transfer impractical in existing point-to-multipoint communication systems.
While the existing methods and systems for point-to-multipoint communication systems are sufficient for their stated purpose, they are not sufficient to accurately account for changes in a characteristic of the communication channel during communication service. Thus, improved methods and systems are needed.